In a post entitled "Protect the seemingly useless", Katja Grace approvingly quotes the following, by G.K. Chesterton:
In the matter of reforming things, as distinct from deforming them, there is one plain and simple principle; a principle which will probably be called a paradox. There exists in such a case a certain institution or law; let us say, for the sake of simplicity, a fence or gate erected across a road. The more modern type of reformer goes gaily up to it and says, “I don’t see the use of this; let us clear it away.” To which the more intelligent type of reformer will do well to answer: “If you don’t see the use of it, I certainly won’t let you clear it away. Go away and think. Then, when you can come back and tell me that you do see the use of it, I may allow you to destroy it.”Let's start by saying explicitly something which is only implicit in the quote*: The rational part of political disagreement can have two components; (i) disagreement about the consequences of a political measure and (ii) disagreement about how potential consequences should be valued. This implies that people can be bad in at least two different senses of the word: They can be incompetent (harboring incorrect assumptions about the consequences of political measures) or they can be evil (holding values which are very different from ours). To illustrate, the Nazis were evil (they wanted to kill lots of Jews) and competent (they managed to do so), while Marx was benevolent (he wanted to improve poor people's lots) but incompetent (his theory was crap).**
This paradox rests on the most elementary common sense. The gate or fence did not grow there. It was not set up by somnambulists who built it in their sleep. It is highly improbable that it was put there by escaped lunatics who were for some reason loose in the street. Some person had some reason for thinking it would be a good thing for somebody. And until we know what the reason was, we really cannot judge whether the reason was reasonable. It is extremely probable that we have overlooked some whole aspect of the question, if something set up by human beings like ourselves seems to be entirely meaningless and mysterious. There are reformers who get over this difficulty by assuming that all their fathers were fools; but if that be so, we can only say that folly appears to be a hereditary disease. But the truth is that nobody has any business to destroy a social institution until he has really seen it as an historical institution. If he knows how it arose, and what purposes it was supposed to serve, he may really be able to say that they were bad purposes, that they have since become bad purposes, or that they are purposes which are no longer served. But if he simply stares at the thing as a senseless monstrosity that has somehow sprung up in his path, it is he and not the traditionalist who is suffering from an illusion.
Let's for the moment accept the assumptions that (i) the institution in question is of human design and (ii) the designers were competent. This does not settle the issue whether the institution should be abolished. Rather, this raises the question how we assess the designers' values. If we do not know them, we'll have to make assumptions. To stick with the fence example, we may not know why exactly our ancestors errected the fence, but we may know that they valued the well-being of the people on the other side of the fence much less than the well-being of the people on this side. We might conclude that they erected the fence so the people from the other side (where there are often food shortages) could not pick fruit from the trees growing on this side. If we disagree with our ancestors' relative valuation of the well-being of people on this and the other side of the fence, we may come to the conclusion that it may be best to tear down the fence.
More generally, the assumption that the designers of institutions were competent should not be the end of the debate about the merit of their products, but rather the starting point. For if we believed the designers to have been completely incompetent, the consequences of their products should be assumed to be neutral on average. If we believe them to have been competent, the default assumption according to Chesterton should be that he designers were benevolent - the reformer must show that the purposes served "were bad purposes" - but I don't see any general reason why this should be so.
The argument that we should be careful to mess with established institutions usually comes in a somewhat different flavour. In this view, it is irrelevant whether the institution in question is a product of conscious design and, if it is, what the designers were thinking. Elsewhere, I've called it The Basic Conservative Fallacy, denoting the view
that just because Feature X has been around for long means that it is better than alternatives. This is nonsense. All it shows is that societies which exhibit Feature X can be able to survive for a nontrivial amount of time. That's it. The age of a feature says nothing about its quality. The changed or new feature may be worse. It may be better. We need to assess it on its own prospective merits, and the fact that there is a lot of uncertainty involved in so doing does nothing to counter these arguments.But, it might be said, a society surviving for a nontrivial amount of time is not nothing. True, few changes of institutions bring about the collapse of a society (however defined). But, although unlikely, it is a very grave consequence (in expected value terms, the product of p and U is nontrivial).
Even short of a collapse of society, it is said, changing institutions may bring about vast negative consequences that were not foreseen. For example, here's Megan McArdle, who thinks about gay marriage, also quotes the bit by Chesterton above approvingly, and outlines what she sees as three important negative consequences of well-meant changes to institutions.*** Changes to institutions may indeed bring about unintended negative consequences, but to say any more would be to commit what, while I'm at it, I'll call The Unintended Consequences Fallacy: the view that changes made will bring about unintended consequences of note and that unintended consequences, on net, will be negative. If this were so, it would be a very powerful blanket argument against changes, but there is no reason to believe it is indeed so. Also, let's not forget that changes in institutions usually lead to the intended consequences, which usually is not trivial either.
Finally, let's note that in many cases we have reliable information that our ancestors, many of whom were no fools, held values different from ours (especially different attitudes towards members of outgroups) and that many of the institutions they designed were in line with these values (i.e., the ancestors were competent and evil). If it is now unacceptable to promote such values in public discourse and discussants defend such institutions, but doing so using a currently acceptable value system, it does not automatically follow that their arguments are wrong, but it should make us especially critical of these arguments. Maybe the discussants are not being fully honest about the real reasons for their defense of the institutions.
Update: Funny this: A few hours after finishing this text, I come across a post by Robin Hanson arguing we have an inherent tendency to prefer existing institutions.
Disclaimer: Neither of Katja Grace's links gives more context for the quote, so I have not seen any.
*A less polite way of putting this would be to say that Chesterton does his best to obscure the distinction between the two.
**This is an illustration. Please, no comments about Marx's real intentions, how Jews could have been killed more effectively, and the like.
***There's much in the essay I disagree with. There's also a lot I agree with. I recommend reading it.